WiFi may operate in distinct frequency ranges (e.g., 2.4 GHz, 3.6 GHz, and 4.9/5.0 GHz). Each range may be divided into a multitude of channels. Individual countries may regulate the allowable channels, allowed users, and maximum power levels within frequency ranges. However, regulations may not be consistent from country to country. Accordingly, spectrum assignments and operational limitations are not consistent worldwide. For example, the United States 2.4 GHz band may allow use of channels 1 through 11, while much of Europe allows for an additional two channels (e.g., channels 12, and 13) beyond those permitted in the United States. Japan further allows communication on channel 14.
A WiFi signal can occupy five channels in the 2.4 GHz band and the protocol can require 25 MHz of channel separation, with adjacent channels overlapping and possibly interfering with each other. Therefore spacing of at least 5 channels (or more) between each WiFi network is desirable to avoid interference. Channels 1, 6, and 11 are three non-overlapping channels in the United States and popular choices for use in WiFi stations. In other counties, other channels may be designated as non-overlapping channels. In parts of Europe and Japan for example, channels 1, 5, 9, and 13 may be designated as non-overlapping channels. In contrast, the 5 GHz range may have 23 non-overlapping channels.
To discover WiFi access points or stations traditionally requires scanning all channels (e.g., channels 1 through 13 or 14). Devices are typically agnostic to geographic location. Especially in the case of WiFi based positioning systems (WPS), discovery channel scans can occur frequently. Each WPS discovery scan uses power and CPU cycles, which may be detrimental to battery life for mobile devices.
Therefore, new and improved power and processing efficient channel scanning mechanisms are desirable.